In the field of magnetic memories represented by hard disk drives (HDDs), research has been actively conducted on a recording method involving the use of heating means using a light beam, for the purpose of achieving higher bit density.
For example, Patent Literature 1 (Japanese Patent Application Publication, Tokukaihei, No. 4-176034 A; Publication Date: Jun. 23, 1992) discloses, as a technology for high-density magnetic read/write, a magnetic recording medium including a recording layer made of an n-type ferrimagnetic material having a compensation temperature substantially equal to room temperature, and also discloses an optically assisted read/write system using a light beam and the above medium.
According to the above system, recording is performed by heating a local portion of the magnetic recording medium by light irradiation, i.e., by providing optical assistance. This reduces the coercive force of the local portion and thereby allows a magnetic head to perform recording. As described above, the optically assisted read/write system allows data to be recorded on a magnetic recording medium having a high coercive force as compared to the intensity of a magnetic field generated by a magnetic head. In the case of a magnetic recording medium having a high coercive force, the above arrangement further prevents the problem of heat fluctuation, thereby allowing ultrahigh-density magnetic recording. The “problem of heat fluctuation” herein refers to a problem of loss of data recorded on a magnetic recording medium, the loss being caused when heat energy of room temperature, for example, disturbs the magnetization direction of the magnetic recording medium.
Further, a method is proposed as an application of the above optically assisted read/write system. The method uses near-field light as a light beam for forming smaller magnetic bits so that recording is performed with higher density. This method allows an area of a magnetic recording medium, the area having a temperature elevated by optical assistance, i.e., a spot of illumination by the near-field light, to have a diameter of several tens of nm or less. This in turn allows for formation of a magnetic bit of several tens of nm or less in size. Consequently, this method enables ultrahigh-density recording.
One disclosed example of the above magnetic head is a magnetic head (information recording and reproduction head) including an electromagnetic field generating element that includes: a substrate serving as a slider; a semiconductor laser section disposed on the substrate and serving as a light source; and a conductor section disposed on the substrate and having a constricted portion. The electromagnetic field generating element, disclosed in Patent Literature 2 (Japanese Patent Application Publication, Tokukai, No. 2004-303299 A; Publication Date: Oct. 28, 2004), includes: a light source; a conductor having a constricted portion in which an electric current path is narrowed; and a substrate on which the conductor is disposed in the form of a layer. Irradiation of the constricted portion with light from the light source generates a near-field light in the constricted portion.
Patent Literature 3 (Japanese Patent Application Publication, Tokukai, No. 2002-298302 A; Publication Date: Oct. 11, 2002) discloses a magnetic head (optically assisted magnetic recording head) that includes a pair of structures (preferably, soft magnetic bodies) separated by a gap and that applies a near-field light and a magnetic field from the gap.